I'd like to be able to set up a computer as a baby monitor using the microphone to send sound to other computers in the house.

Now before anyone says "Just buy a baby monitor" I don't have a baby

I expect there is some software out there that will do the job but I have not been able to find it. I expect it is more because I do not know what to search for. I keep finding "Streeming Software" but it seems to all be about recieving audio.

You know, I'll bet you could set up a computer with an inexpensive web cam as a baby monitor. You'd have sound and video and you could adjust the frame rate and size so it wasn't much of a burden on the system. I know Linux has home surveilance software.